Method for determining a coverage area in a cell based communication system

ABSTRACT

A method ( 300 ) determines a per-cell coverage area in a cellular communication system that comprises multiple cells. The method comprises measuring ( 305 ) one or more parameters relating to one or more operations of a first cell in a cellular communication system. The method includes calculating ( 320 ) a degree of coverage overlap from a number of measurements, preferably by comparing a number of first measurements relating to a location that is uniquely served, with a number of second measurements that can be served by a plurality of serving communication units. Tn this manner, it is possible to determine an amount of overlapping coverage area based on real network measurements rather than inaccurate predicted data that has been t—aditionally employed. Preferably, the measurements afe converted to Erlangs to provide a coverage overlap based on subscriber traffic. A communication system ( 100 ) and a communication unit ( 146 ) are also provided.

FIELD OF THE INVENTION

This invention relates to determining the coverage of a cell in acell-based communication system. The invention is applicable to, but notlimited to, utilising such coverage information to assist alarmprioritisation due to cell outage and/or re-configure a system's orcell's operational parameters to minimise the degree of overlappingcoverage, thereby allowing higher capacity/quality frequency plans to bedeployed.

BACKGROUND OF THE INVENTION

Wireless communication systems, for example cellular telephony orprivate mobile radio communication systems, typically provide for radiotelecommunication links to be arranged between a plurality of basetransceiver stations (BTSs) and a plurality of subscriber units, oftentermed mobile stations (MSs).

In a wireless communication system, each BTS has associated with it aparticular geographical coverage area (or cell). Primarily, a particulartransmitter power level defines a coverage area where a BTS can maintainacceptable communications with MSs operating within its serving cell. Inaddition, receiver sensitivity performance of receiving wirelesscommunication units also affects a given coverage area. In largecellular communication systems, these cells are combined and oftenoverlapped to produce an extensive coverage area.

Wireless communication systems are distinguished over fixedcommunication systems, such as the public switched telephone network(PSTN), principally in that mobile stations move between coverage areasserved by different BTS (and/or different service providers) and, indoing so, encounter varying radio propagation environments.

In a cellular system, adjacent cells are typically configured tooverlap, to ensure a contiguous signal coverage area. The cell overlapregion is deliberately designed into the system plan to ensure thatmobile stations can successfully handover between cells. The degree ofcoverage overlap between cells can vary enormously. In such systems itis desirable to have an accurate measure of unique cell coverage (andideally cell overlap) to operate and maintain the network moreeffectively (i.e. maximising capacity and quality of service).

A system design based on cells is typically based on an ideal cellpattern. However, an idealised cell pattern never occurs in practice,due to the nature of the terrain and the fact that cell sites andantennae are not ideally located on a regular grid pattern. The networkdesigner therefore uses frequency planning tools to estimate the radiopropagation for each cell and predict a corresponding coverage area.Based on these propagation models, the network designer is able todevelop a frequency plan for the network intended to minimise theexpected interference. The frequency plan considers such factors asantenna heights and location, terrain topology, transmitted power levelsand the anticipated number of subscribers.

By collating predicted coverage area information for a number of cells,it is possible to determine a degree of coverage overlap between anumber of respective cells. However, the accuracy of these tools islimited, since they ‘predict’ the theoretical coverage rather thanmeasure the actual coverage supported by a particular BTS.

The quality of a frequency plan that can be produced by such coverageprediction techniques is constrained by the degree of coverage overlapbetween cells. Greater overlap means greater potential interference,making it more difficult to produce a low interference frequency plan. Atraditional method of allocating frequencies in a wireless cellularsystem is to employ a channel allocation algorithm in conjunction with acarrier-to-interference (C/I) matrix, where the C/I matrix may usemeasurement report data.

Achieving an optimum frequency plan is therefore dependent on the C/Imatrix accuracy, and it is inaccuracies, in these matrices thatultimately lead to unexpected interference. There are a number ofreasons why traditionally produced matrices are inaccurate. For example,the matrices are based on predicted interference levels at ground level,i.e. subscribers in high buildings are not considered. They assume fixedcell boundaries whereas the characteristics of MSs and handoveralgorithms are such that cell boundaries can move. Also, they arereliant on accurate site and antenna data. This data can be far fromaccurate with some Operators having no clear idea of where their sitesare, let alone being confident in the bore angles of the antennas. Theydo not reflect the impact of detailed clutter data, such as streetcanyons.

Furthermore, these coverage prediction techniques tend to focus ongeographic coverage area, assuming an even distribution of MSs withinthe cell, rather than subscriber-based coverage where subscribers areunevenly distributed across a cell. This inaccuracy limits theeffectiveness of the predictions and the resulting decisions madetherefrom. This, in turn, means that the network is sub-optimallyconfigured and therefore typically delivers a sub-optimal quality ofservice.

The inventors of the present invention have therefore both recognisedand appreciated that there is currently no accurate method ofdetermining an accurate cell-based coverage map, particularly when thereexists coverage overlap between cells.

In the context of network optimisation, it is known that measurementreports are collected from an operational network, as described inco-pending UK Patent Application GB 9926513.4 having the same Applicantas the present invention. The data collected is then analysed togenerate neighbour cell list for handover purposes and facilitate powercontrol decisions. In this regard, it is known that MSs scan signaltransmissions from multiple BTSs and report the signal levels of thesein the measurement reports. The scanning process, which is used togenerate the measurement reports, enables the MS (or its serving BTS) todetermine optimal handover candidates, namely the BTS offering thehighest quality signal/communication link to the respective MS.

Thus, there exists a need in the field of the present invention toprovide a cell-based communication system and method for determiningcoverage overlap in a cell-based communication system, wherein theaforementioned disadvantages may be alleviated.

STATEMENT OF INVENTION

In accordance with a first aspect of the present invention there isprovided a method of determining coverage in a cellular communicationsystem, as claimed in Claim 1.

In accordance with a second aspect of the present invention, there isprovided a storage medium, as claimed in Claim 10.

In accordance with a third aspect of the present invention, there isprovided a communication system, as claimed in Claim 11.

In accordance with a fourth aspect of the present invention, there isprovided a communication unit, as claimed in Claim 12.

In summary, the inventive concepts of the present invention propose amechanism for using measurement reports (MRs) to determine the uniquecoverage and the potential interfering (overlapping) coverage generatedby each cell, preferably determined in terms of Erlangs. By utilisingMRs in this manner, the Network Operator is able to direct andprioritise both automatic and manual maintenance and optimisationactivities, for example, alarm prioritisation to distinguish the morecritical coverage cells. Alternatively, or in addition, the coveragecalculations, according to the preferred embodiment of the presentinvention, may be used to re-configure a system's operationalparameters, such as: transmit power, a beam-forming antenna tilt ordirection, and even turning off cell sites whose excessive coverageoverlap provides unacceptable interference or severely restricts thefrequency allocation process.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will now be described,with reference to the accompanying drawings, in which:

FIG. 1 illustrates a block diagram of a cellular radio communicationssystem adapted to support the various inventive concepts of a preferredembodiment of the present invention;

FIG. 2 illustrates a cell-based communication system adapted to supportthe various inventive concepts of a preferred embodiment of the presentinvention; and

FIG. 3 illustrates a flowchart of a method of determining an overlappingcoverage area, and thereafter utilising such information, in accordancewith a preferred embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive concepts of the present invention propose a mechanism forusing measurement reports (MRs) to determine both the unique andoverlapping (and therefore interfering) coverage generated by each cell.In particular, three aspects of a respective cell's coverage may bedetermined:

-   -   (i) The amount of traffic that receives coverage uniquely from        this cell;    -   (ii) The amount of traffic that receives coverage from this        cell, but which could also obtain coverage from an adjacent        cell; and    -   (iii) The amount of traffic carried by adjacent cells that could        provide coverage to this cell.

From a perspective of a serving cell, at one extreme, it is known thatthe coverage area of the cell may be completely overlapped by one ormore adjacent cells. At the other extreme, the coverage area of twocells may be configured to not overlap at all. This variation hassignificant implications for system operation. For example, if a cellgoes off-air, then subscriber units in the area uniquely covered by thiscell will no longer have service. However, if there is a large degree ofoverlap from neighbouring cells, then many subscriber units will be ableto receive service from neighbouring, but less-preferred, cells.Conversely, with no overlap, all subscriber units will lose service.

Hence, in accordance with a preferred embodiment of the presentinvention, a mechanism to determine an accurate knowledge of coverageoverlap is proposed. Once an accurate knowledge of coverage overlap hasbeen determined the relative importance of keeping various cells on aircan be identified.

The inventors of the present invention have appreciated that those cellsproviding the most unique coverage are the most critical to bemaintained. Therefore, for example in a first embodiment of the presentinvention, the resulting cell outage alarm should be set to reflect theuniqueness and importance of the cell. Furthermore, in a secondembodiment of the present invention, such knowledge also helps determinenetwork availability as well as enabling a Network Operator to setoptimum system parameters. Furthermore, such knowledge enables highercapacity and better quality frequency plans to be deployed.

From a perspective of a neighbouring, overlapping cell, at one extreme,the cell may overlap with many neighbouring cells. Alternatively, thecell may overlap with no other cells. This variation impacts frequencyplanning, since the frequencies assigned to a cell with large overlapcannot be re-used in the overlapped cells, making frequency planningmore difficult. However, a cell with a largo overlap may be useful forproviding continuity of service, should the overlapped cells go out ofservice or become congested.

The inventive concepts of the present invention alleviate theaforementioned problems associated with the coverage prediction byextending the concept of an Intelligent Optimisation Service (IOS), asdescribed later. In particular, the present invention proposes amechanism of using existing measurement reports to assist in determininga level of coverage overlap. Furthermore, once such measurement reportshave been received and processed and coverage overlap information hasbeen calculated, the information can be used in a variety of ways, asdetailed later.

Referring first to FIG. 1, a cellular telephone communication system 100is shown, in outline, supporting a Global System for Mobilecommunication (GSM) air-interface, in accordance with a preferredembodiment of the invention. The European Telecommunications StandardsInstitute (ETSI) has defined the GSM air-interface.

Generally, the air-interface protocol is administered from basetransceiver sites, within the network architecture 110, that aregeographically spaced apart—one base site supporting a cell (or, forexample, sectors of a cell), as shown in FIG. 2.

A plurality of subscriber units 112-116 communicate over the selectedair-interface 118-120 with a plurality of base transceiver stations(BTS) 122-132. A limited number of MSs 112-116 and BTSs 122-132 areshown for clarity purposes only. The BTSs 122-132 may be connected to aconventional public-switched telephone network (PSTN) 134 through basesite controllers (BSCs) 136-140 and mobile switching centres (MSCs)142-144.

Each BTS 122-132 is principally designed to serve its primary cell, witheach BTS 122-132 containing one or more transceiver units andcommunicating 156-166 with the rest of the cellular systeminfrastructure

Each BSC 136-140 may control one or more BTSs 122-132, with BSCs 136-140generally interconnected through MSCs 142-144. Processes within the MSCsare provided to account for the situation where a MS (112-116) passesbetween-two BTS serving areas, for example MS 112 moving from an areacovered by BTS 122 to an area covered by BTS 124, where the two BTSs arecontrolled by different BSCs (BSC 136 and BSC 138 in this example).

Similar processes are supported in MSCs to account for the situationwhere an MS moves between serving BTSs where these BTSs are connected todifferent MSCs. These mechanisms therefore allow the cellular telephonecommunication system to support handover of MSs 112-116 betweenoverlapping cells in a contiguous, seamless manner.

Each MSC 142-144 provides a gateway to the PSTN 134, with MSCs 142-144interconnected through an operations and management centre (OMC) 146that administers general control of the cellular telephone communicationsystem 100, as will be understood by those skilled in the art.

The various system elements, such as BSCs 136-138 and OMC 146, includecontrol logic 148, 150, 152, with the various system elements usuallyhaving an associated memory function 157 (shown only in relation to OMC146 for the sake of clarity). A memory function 157 of the OMC 146typically stores historically compiled operational data as well asin-call data, system information such as neighbouring cell-site listsand control algorithms such as a list of frequencies to be scanned bythe respective MSs.

In accordance with the preferred embodiment of the present invention,the OMC or an optimisation function adjunct to the OMC 146 receivesMeasurement Reports (MR) collected from respective cells, either from,say, serving BTSs and/or served MSs. In the context of the presentinvention, it is envisaged that an OMC's handling of MRs may becomplemented or replaced by any such adjunct optimisation function. Assuch, the following description of the OMC's functionality in thisregard encompasses any such suitable configuration. Notably, the OMC 146has been adapted to include an overlapping coverage calculation function155. The overlapping coverage calculation function 155 utilises the MRdata to determine those cells that provide a unique coverage to MSswithin those cells. The overlapping coverage calculation function 155also utilises the MR data to determine those cells where some coveragecan be supported by neighbouring cells.

In this regard, the OMC is able to calculate an amount of overlappingcoverage. The OMC 146 has been configured to receive anyoperational/environmental data provided by the system elements or UEsrelating to the operational characteristics of the respective cells, inorder to determine, for example, a level of unique coverage thatrespective cells provide.

In a further enhanced embodiment of the present invention, one or moreBSCs 136 and/or one or more BTSs 122 may include, or be operably coupledto, an MR agent (not shown). The BSC 136 or BTS 122 preferablyconfigures the agent to seek out and record measurements for therequisite environmental or operational data that may affect theoverlapping coverage area of the cell.

It is also envisaged that the cell's MR information may be sent from anynumber of sources and include any useful data. In particular, theinformation may include:

-   -   (i) Cell statistical information, available at the OMC, such as        Congestion, Blocking, Mean-Hold Time (MHT), landover (HO) Cause        distribution;    -   (ii) Measurement Reports, which indicate the Radio Frequency        (RF) environment of the subscriber units; or    -   (iii) Control Signalling behaviour. This information is readily        available to the OMC function in existing systems. It forms the        basis of reports generated for the Network Operator to analyse        during the course of normal operational activities.

In particular, if a MR from a MS contains no neighbouring BTSmeasurements, or only very weak neighbour measurements, it can beassumed that the MS could not achieve service from any neighbouringcell. This information is particularly useful to the OMC 146, shouldthat serving cell go off-air or become congested.

Conversely, if the MR contains one or more neighbour measurementsindicating a strong received signal, then it can be assumed that the MScould obtain service from one of these neighbours, if its serving cellbecomes unavailable. Thus, by analysing all the MRs collected from aparticular cell, it is possible to determine, for example, a proportionof the cell's traffic that depends solely on that cell for service. Inthis context, the OMC 146 is able to determine an unique coverage factorfor that cell (UCF), where: $\begin{matrix}{{UCF} = \frac{{Sum}\quad{of}\quad{MRs}\quad{with}\quad{no}\text{/}{weak}\quad{neighbours}}{{Total}\quad{Sum}\quad{of}\quad{MRs}}} & \lbrack 1\rbrack\end{matrix}$

In the context of the present invention, a weak neighbour is defined,for example, as a neighbour reported with a received signal level(RXLEV) of < ‘X’, where ‘X’ can be set by the Network Operator, forexample, set at an RXLEV of ‘10’ (equivalent to, say, −100 dBm).

In the enhanced embodiment of the present invention, the OMC 146comprises an overlapping coverage calculation function 155 togenerate/calculate a subscriber-based coverage map that particularlyindicates coverage overlap.

Preferably, the calculation to determine the degree of overlappingcoverage is based on the number of times that a cell is reported as aneighbouring cell, by subscriber units in the other network cells.Indeed, in accordance with the preferred embodiment of the presentinvention, this information can easily be extracted from existingmeasurement report information. In this regard, acarrier-to-interference (C/I) matrix of rows and columns is produced,where each column represents the potential interference generated by aspecific cell.

A simplified example of such a matrix is illustrated below in Table 1.The rows represent the cells ‘A’-‘D’ as serving cells, and the columnsrepresent cells ‘A’-‘D’ as interfering cells. For example, cell ‘B’ canexpect to lose six Erlangs of traffic due to interference, if it has thesame frequency as cell ‘C’. Hence, the amount of coverage overlapgenerated by each cell, which could potentially lead to interference, isrepresented by the total of the column for the respective cell. Thus, inthis example, Cell ‘B’ has the highest overlap with forty Erlangs oftraffic seen in other cells at a strong level. TABLE 1 A B C D A 1 10 510 B 12 6 10 C  5 15 17 D  7 15 5 Total 24 40 16  37

Advantageously, the use of Measurement Reports ensures that ‘real’measurement data from the actual operating network is used, in contrastto the known technique of using inaccurate prediction data. By ensuringthat a statistically significant volume of Measurement Reports are usedin the calculations, it is possible to guarantee that the resultingmeasures or calculations of unique cell coverage and cell overlap areextremely accurate. These values represent the cell coverage and overlapfrom the perspective of all the network subscriber units. Consequently,the impact on the network subscriber units, of decisions made using thisdata, can be accurately determined.

In accordance with the preferred embodiment of the present invention,the memory element 157 of the OMC 146 has also been adapted to include,for example, a look-up table of the coverage overlap information. Inthis regard, the look up table contains information relating to one ormore of the-following:

-   -   (i) Cell operational parameters,    -   (ii) Threshold values used in the respective cell(s),    -   (iii) Traffic profile information for that cell,    -   (iv) Received signal level information, say from a number of        MSs, for that cell—irrespective of whether the MSs are being        currently served in that cell, or    -   (v) Transmitter power information, for either BTS and/or MS,        relating to a particular cell.

Although the inventive concepts of the present invention have beendescribed with regard to an implementation in an OMC 146, it is withinthe contemplation of the invention that the overlapping coveragecalculation function 155 may be provided in a separate device orfunction, operably coupled to the OMC 146. Alternatively, theoverlapping coverage calculation function 155 may be located within anyother element within tine infrastructure, such as MSCs 142, 144, orwithin BSCs 136, 138, 140 or even distributed within a number ofelements, if appropriate. For example, the overlapping coveragecalculation function 155 could be implemented within the radio accessnetwork (RAN) of the cellular infrastructure equipment and/or it may beimplemented as a stand-alone element/function on an adjunct platform.Indeed, it is envisaged that the OMC as a logical entity could compriseseveral distributed or substantially co-located boxes with specificfunctions, including an optimisation (IOS) box.

In a preferred embodiment of the present invention, it is also envisagedthat one or more BTSs 122-132 and/or one or more BSCs 136-140 may beadapted to regularly or intermittently collect the MR data. Thisinformation would then be forwarded to the OMC 146 (or indeed any otherassociated element) where the overlapping coverage areamapping/calculation function 155 resides.

More generally, an overlapping coverage calculation function 155 may beprogrammed into, say, the OMC 146 according to the preferred embodimentof the present invention, in any suitable manner. For example, newapparatus may be added to a conventional communication unit (for exampleOMC 146). Alternatively existing parts of a conventional communicationunit may be adapted, for example, by reprogramming one or moreprocessors therein. As such the required adaptation may be implementedin the form of processor implementable instructions stored on a storagemedium, such as a floppy disk, hard disk, programmable read only memory(PROM), random access memory (RAM) or any combination of these or otherstorage media.

Referring now to FIG. 2, a cell-based communication system 200, adaptedto support the various inventive concepts of a preferred embodiment ofthe present invention, is illustrated. FIG. 2 is a representation of,say, a street level coverage map from Cells A 210, B 220, C 230, D 240,E 250, F 260 and X 270. As with a vast majority of cell-based wirelesscommunication systems, there is significant degree of overlap betweencell coverage areas. A key illustration in FIG. 2 is that although thecoverage area of Cell X 270 is significant, most of its coverage couldbe supplemented by coverage from neighbouring cells ‘A’ to ‘F’ 210-260.The proportion of unique coverage that is solely supportable by cell X270 is an island of coverage at the centre of cell X 270. Any subscriberunits located in this region would definitely suffer a complete outageif Cell X 270 were to go out of service.

Although FIG. 2 illustrates the geographical coverage impact of such anoutage, a key benefit of the present invention is to determine a numberof Erlangs of traffic that would be lost due to the outage. For example,let us assume that only 10% of the cell's coverage area is uniquelyserved by this cell.

However, if all the subscriber units in the cell are concentrated inthis one small central area, then the impact of a cell outage will be toremove service from 100% of the cell's traffic, not just 10% thatrelates to the geographical impact. Thus, it is the Erlang value relatedto impacted traffic that is preferably used in, for example:

-   -   (i) Prioritising a resulting outage alarm, and/or    -   (ii) Re-configuring a system's operational parameters.

In an enhanced embodiment of the present invention, the potentialinterference generated by cell X 270 on neighbouring cells ‘A’-‘F’210-260, based on a level of overlap between the cells, may be used todetermine whether to re-configure cell X's operational parameters. Forexample, the transmit power of cell X 270 may be reduced, or antennadown-tilting of Cell X's beam-forming antenna introduced.

Referring now to FIG. 3, a flowchart 300 illustrates an overview of thepreferred overlapping coverage measurement process. The flowchartcommences with an OMC (or other box) collecting a series of MeasurementReports (MRs), for example resulting from a subscriber unit pollingoperation, as shown in step 305. MRs are collected from the target celland from its neighbouring cells.

These MRs are then separated into, say, three categories, in step 310:

-   -   (i) Those MRs for which an alternative cell is identified as        being able to provide coverage;    -   (ii) Those MRs for which there is no alternative coverage        option, i.e. the subscriber unit generating the MR can only        be-served by that cell in that location; and    -   (iii) Those MRs collected from neighbouring cells that show a        strong level of coverage from the target cell.

The OMC then converts the MR information into Erlangs, in step 315, todetermine the traffic impact, rather than the geographical impact, ofany potential cell outage. These results may then be stored, in step325, according to the time of day, day of the week, month and anyadditional cell parameter information such as transmit power, andsubscriber unit information such as cell location (say, from a GPSunit). In the illustrative step 325, the results are stored againstfour-hour intervals for each day of the week: however clearly theresults may be stored using any storage/sorting method determined by askilled person.

Thus, in this manner, an OMC determines how much traffic coverage isuniquely provided by a particular cell, for example, using existingmeasurement report data. Preferably, a statistically valid sample of MRsis used in the determination of overlapping and/or unique coverage. Oncean Erlang figure has been determined, this figure is used to influencethe Network Operator (or the OMC) to improve the network's performance.

For example, the figure is used to determine an appropriate cell outagestrategy, in step 330. It is envisaged that such a use may entaildetermining when and how to maintain a cell, i.e. by turning the celloff. The traffic impact of such cell maintenance can therefore beminimised. Furthermore, the cell outage strategy may encompass the OMCusing the Erlang value of uniquely covered traffic to select an alarmpriority setting for the cell, as shown in step 340.

Advantageously, the unique coverage capability and coverage overlapinformation of the cell can also be used to automatically re-configureoperational parameters in a cell, as shown in step 335. Such are-configuration of operational parameters helps determine and implementa feasibility of beam-forming changes such as down-tilts, provision ofadditional redundancy, etc.

The inventive concepts of the present invention utilise dynamicmonitoring and adaptation of a cell's operational parameters. Suchinformation, when obtained extensively throughout the system, may beassessed to better plan and utilise available communication resources(frequencies) throughout the system. In this manner, it is envisagedthat an automatic frequency planning operation may benefit from theinventive concepts described herein.

It is within the contemplation of the invention that the OMC 146 may useany additional indicia, such as traffic load, time of day, etc. toenhance the assessment of communications within the communicationsystem. It is also envisaged that the OMC 146 (or other element) maypoll BTSs or MSs within the system to obtain such additional indicia.Further variations that fall within the inventive concepts hereindescribed will be apparent to a person skilled in the art.

The preferred embodiment of the present invention has been describedwith regard to a cellular telephony communication system, such as theglobal system for mobile communications (GSM). It is envisaged that theinvention is equally applicable to other wireless communication systems,such as a universal mobile telecommunication system (UMTS), any codedivision multiple access (CDMA) or time division multiple access (TDMA)system, or an integrated digitally enhanced network (iDEN)™ as suppliedby Motorola™. It is also within the contemplation of the invention thatalternative radio communication architectures, such as private or publicmobile radio communication systems could benefit from the inventiveconcepts described herein.

It will be understood that the communication system, communication unit,and improved method for coverage prediction, as described above,provides at least some of the following advantages that could not bereliably obtained using existing coverage prediction methods:

-   -   (i) Cells with high unique cell coverage are recognised as such,        and may be managed more carefully. For example, a Network        Operator may decide to introduce additional equipment redundancy        into a particular system to minimise the risk of cell outage.    -   (ii) Cells with low unique cell coverage can be configured to        receive less attention. In some cases, if capacity is not        required, it may even be desirable to switch the cell off.    -   (iii) The aforementioned principles can be extended to encompass        the level of unique coverage provided by a group of cells (e.g.        a BSC area), or the level of unique coverage provided by a        particular sub-layer or frequency band (e.g. a Micro-cell layer,        or a cellular 1800 MHz frequency band)    -   (iv) Cells that provide high levels of coverage overlap provide        severe constraints on the development of a high quality and        capacity frequency plan. Consequently, these cells can be        examined to determine whether the cell's transmit power can be        reduced, the antenna down-tilted, or the cell completely        switched off.

Whilst the specific and preferred implementations of the embodiments ofthe present invention are described above, it is clear that a skilledartisan could readily apply variations and modifications of suchinventive concepts.

Thus, a communication system, a communication unit, and a method forcoverage prediction have been provided wherein the aforementioneddisadvantages associated with prior art arrangements have beensubstantially alleviated.

1. A method of determining per-cell traffic coverage in a cellularcommunication system that comprises multiple cells, the methodcomprising the steps of: receiving measurements of parameters relatingto one or more operations of a first cell in a cellular communicationsystem, wherein said parameters include information relating to how manyand which cells serve a wireless subscriber communication unit; andcalculating a degree of coverage overlap for said first cell based on anumber of said measurements by partitioning said measurements into atleast one of three categories with respect to the first cell, selectedfrom the group of: (i) A first category where the measurement indicatesa wireless subscriber unit that is uniquely served by the first cell,(ii) A second category where the measurement indicates a wirelesssubscriber unit that can be served by cells other than the first cell,and (iii) A third category where the measurement indicates a wirelesssubscriber unit that is served by a neighboring cell but could be servedby the first cell.
 2. The method of determining per-cell trafficcoverage in a cellular communication system according to claim 1,wherein the step of calculating a degree of coverage overlap based on anumber of said measurements employs a statistically valid sample of saidmeasurements.
 3. The method of determining per-cell traffic coverage ina cellular communication system according to claim 1, wherein the stepof calculating comprises determining a unique coverage factor (UCF) forthat cell using Measurement Reports (MR), where:${UCF} = \frac{{Sum}\quad{of}\quad{MRs}\quad{with}\quad{no}\quad{and}\text{/}{or}\quad{weak}\quad{neighbours}}{{Total}\quad{Sum}\quad{of}\quad{MRs}}$4. The method of determining per-cell traffic coverage in a cellularcommunication system according to claim 1, the method further comprisingthe step of: converting a number of measurements to Erlangs to determinea coverage overlap based on subscriber traffic within said cell.
 5. Themethod of determining per-cell traffic coverage in a cellularcommunication system according to claim 1, the method further comprisingthe step of: allocating a priority to said cell based on saidcalculation.
 6. The method of determining per-cell traffic coverage in acellular communication system according to claim 1, the method furthercomprising the step of: in response to said calculation, re-configuringat least one operational parameter of said cell selected from the groupof; a transmit power, a beam-forming antenna changes, and turning off acell.
 7. The method of determining per-cell traffic coverage in acellular communication system according to claim 1, the method furthercomprising the steps of: storing said calculations; and using saidstored calculation subsequently to determine a cell outage strategy. 8.The method of determining per-cell traffic coverage in a cellularcommunication system according to claim 1, wherein the steps ofmeasuring and calculating are used in an automatic frequency planningoperation of said cellular communication system.
 9. The method ofdetermining per-cell traffic coverage in a cellular communication systemaccording to claim 1, wherein the wireless communication unit receivesmeasurement reports from a wireless serving communication unit selectedfrom the group of; a base transceiver station and a wireless subscribercommunication unit. 10-11. (canceled)
 12. A communication unit for usein a cellular communication system that comprises multiple cells, thecommunication unit comprising: a receiver for receiving measurements ofparameters relating to one or more operations of a first cell in saidcellular communication system; and a processor, operably coupled to saidreceiver, to process said received data, wherein said processorcalculates a degree of coverage overlap based on a number of saidmeasurements by partitioning said received measurements into at leastone of three categories with respect to the first cell, selected fromthe group of: (i) A first category indicating a wireless subscriber unitthat is uniquely served by the first cell, (ii) A second category wherethe measurement indicates a wireless subscriber unit that can be servedby a number of cells, and (iii) A third category where the measurementindicates a wireless subscriber unit that is served by a neighboringcell but is located such that it could be served by the first cell. 13.The communication unit according to claim 12, wherein said processordetermines a unique coverage factor (UCF) for a cell using MeasurementReports (MR), where:${UCF} = \frac{{Sum}\quad{of}\quad{MRs}\quad{with}\quad{no}\quad{and}\text{/}{or}\quad{weak}\quad{neighbours}}{{Total}\quad{Sum}\quad{of}\quad{MRs}}$14. The communication unit according to claim 12, wherein said processorconverts a number of measurements to Erlangs to determine a coverageoverlap based on subscriber traffic within said cell.
 15. Thecommunication unit according to claim 14, wherein said processorallocates a priority to said cell based on said calculation.
 16. Thecommunication unit according to claim 12, wherein in response to saidcalculation, said communication unit is operable to re-configure atleast one operational parameter of said cell.
 17. The communication unitaccording to claim 16, wherein said communication unit configures saidcell for at least one of the group of; transmit power changes,beam-forming antenna changes, and switching off said cell site.
 18. Thecommunication unit according to claim 12, wherein said communicationunit is an operations and management centre configured to receivemeasurement report data relating to cells in said cellular communicationsystem.
 19. The communication unit according to claim 12, wherein saidmeasured data includes at least one of the following: (i) Cellstatistical information including at least one of Congestion, Blocking,Mean-Hold Time (MHT), and Handover (HO) Cause distribution information;(ii) One or more Measurement Reports; and (iii) Control Signallingbehavior.
 20. The communication unit according to claim 12, wherein saidprocessor is operably coupled to a memory device for storing saidcalculations for subsequent use in determining a cell outage strategy.21. The communication unit according to claim 12, wherein saidcommunication unit is able to communicate on at least on of a GSM, GPRS,UMTS, iDEN, and CDMA cellular communication system.